In recent years, an environmental problem has been issued globally with respect to the release of exhaust gases from vehicles. To cope with this, regulations of exhaust gas of a vehicle have been tightened. Vehicle industries have invested enormous capital to develop an exhaust system for removing harmful ingredients included in exhaust gas and have conducted many studies for a method for reducing harmful gas and enhancing fuel consumption.
As one of the methods for reducing harmful gas, an after treatment device for purifying exhaust gas, for example, a diesel particulate filter (DPF) for reducing particulate materials (PMs) and nitrogen oxide (NOx), a diesel oxidation catalyst (DOC), and selective catalytic reduction (SCR) have been used in the exhaust system.
The after treatment device has used metal materials such as platinum and palladium as a catalyst. To activate the catalyst, the supplied exhaust gas needs to be maintained at a predetermined temperature or more.
However, this conventional art takes much time to increase a temperature of the catalyst using exhaust gas after an engine starts. Therefore, conventional art requires a method for increasing temperature by injecting fuel to an after treatment device, a method for using an electric heater, or the like. Thus, conventional methods have a problem in that fuel consumption of a vehicle deteriorates.
In addition, we have discovered that the conventional methods may excessively discharge the exhaust gas including a large amount of harmful ingredients due to an activation time delay of the catalyst since heat is discharged to the outside while the high-temperature exhaust gas combusted in the engine passes through an exhaust port, an exhaust manifold, and the after treatment device.
Further, conventional methods use heat energy to heat canning (generally referred to as a “cover” in the art) enclosing the catalyst of the after treatment device and therefore causing energy loss (heat loss) independent of the catalyst activation.
Conventional methods also require durability of the canning of the after treatment device that may bear the high temperature environment, and therefore may increase costs because the canning is made of a relatively expensive material.
The preceding information is meant only for enhancing the understanding of the present disclosure and therefore it may contain information that does not form part of the prior art that is already known in this field to a person of ordinary skill.